Co(phen)3(PF6)3

Technical Specifications

Product Description & Scientific Applications

Tris(1,10-phenanthroline)cobalt(III) tris(hexafluorophosphate) is the hexafluorophosphate salt of the [Co(phen)₃]³⁺ cation, in which cobalt(III) is chelated by three bidentate 1,10-phenanthroline ligands to give an octahedral tris-chelate. Like all octahedral tris(bidentate) complexes the cation is chiral, occurring as Δ and Λ enantiomers. As the hexafluorophosphate salt it is soluble in polar aprotic solvents such as acetonitrile, and its solution chemistry is that of the [Co(phen)₃]³⁺ cation.

Redox behaviour. The cobalt(II)/cobalt(III) couple is a one-electron, outer-sphere redox system. The change in oxidation state reorganizes the coordination sphere: averaged over reported [Co(phen)₃]ⁿ⁺ structures the cobalt–nitrogen distance is about 1.95 Å for cobalt(III) and about 2.12 Å for cobalt(II), so reduction lengthens the metal–ligand bonds and oxidation contracts them.

Solar-cell redox mediator. In dye-sensitized solar cells the couple acts as the electrolyte redox mediator: the cobalt(II) form regenerates the photo-oxidized dye, while the cobalt(III) salt — the oxidized half of the shuttle — is reduced again at the counter electrode. Unlike triiodide, the cobalt mediator absorbs little visible light and so does not shadow the sensitizer. Paired with the high-absorption organic dye C218, the phenanthroline shuttle gave an iodine-free cell of 8.3% power-conversion efficiency under full sunlight.

Electron-transfer oxidant. As a defined one-electron oxidant the cation is used to study electron-transfer mechanisms. In acetonitrile it oxidizes verdazyl radicals to verdazylium cations, forming the cobalt(II) complex, along a pathway consistent with Marcus theory; in aqueous acid it oxidizes iodide. These reactions make it a convenient reference oxidant for electron-transfer kinetics.

Metalloprotein oxidant. The cation oxidizes the heme protein ferrocytochrome c. At low ionic strength the reaction is governed by electrostatic association and proceeds through a conformationally open form of the protein, so the complex serves as a probe of protein conformation and biological electron transfer.

Porphyrin template. In acidic solution the cation promotes the self-assembly of the anionic porphyrin tetrakis(4-sulfonatophenyl)porphyrin into J-aggregates by an autocatalytic nucleation-and-growth process.

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